plproxy - plproxy: use drop lang to allow plpgsql exist in template1

Log Message:
-----------
use drop lang to allow plpgsql exist in template1

Modified Files:
--------------
plproxy/expected:
plproxy_encoding.out (r1.5 -> r1.6)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/plproxy/plproxy/expected/plproxy_encoding.out.diff?r1=1.5&r2=1.6)
plproxy/sql:
plproxy_encoding.sql (r1.4 -> r1.5)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/plproxy/plproxy/sql/plproxy_encoding.sql.diff?r1=1.4&r2=1.5)
plproxy_init.sql (r1.4 -> r1.5)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/plproxy/plproxy/sql/plproxy_init.sql.diff?r1=1.4&r2=1.5)